MERCESES BENZ 4MATIC

Chevrolet Impala

I have a 1992 MB 300TE with 4matic. The 4matic yellow light does not go out, so I assume the 4matic is not working. I have had the module tested, it is OK. The transfer case is OK, as is everything else we've checked. Any ideas or suggestions?

I HAVE AN OWNERS MANUAL AND IT INFORMS ME OF A TEST LEVER THAT DE ACTIVATES THE 4 MATIC I PULL IT THE LIGHT COMES ON, AND IT DISABLES THE TRANSFER CASE, ALSO SELF LEVELLING FUCTION, ALSO HAD A LIGHT COME ON AFTER REPLACIONG O V P RELAY ( OVER VOLTAGE )
HAD TO REMOVE 4 MATIC CPU when they put it back I guess the connection was not quite correct I removed and replacxe re/re 4 amtic cpu and light went off hope it helps if your still interested

I have just replaecd all hydraulic oil and transfer case fluids, I realize that if there is any air in the system it may be trapped, mine stayed on and I bled the system at the test valve and now light is back out, and alll is good, hope any info helps